Joined: May 2008
Posts: 10,106
Likes: 2,757
From: Fredericksburg, Va
Bikes: ? Proteous, '65 Frejus TDF, '73 Bottecchia Giro d'Italia, '83 Colnago Superissimo, '84 Trek 610, '84 Trek 760, '88 Pinarello Veneto, '88 De Rosa Pro, '89 Pinarello Montello, 'Litespeed Catalyst'94 Burley Duet, 97 Specialized RockHopper, 2010 Langster
Doesn't look like a "box" rim. The two spokes at the end look like they are the drive side, higher tension. There must have been a stress riser somewhere along the break. If were able to examine the surfaces of the failure, you might be able to see where it started and if there was a any propagation prior to the failure.